The present invention relates to a driver for driving the color filter assembly of a scanner through synchro and in phase controls, permitting the color filter assembly to be positioned accurately.
A variety of scanners are known and widely used in reading color as well as half-tone graphic data. A color scanner generally comprises a color filter assembly driven by a driving mechanism for specifying the colors of a picture being scanned. During the process of scanning, the color filter assembly shall be rotated through synchro control as well as in phase control, so that accurate color separation can be achieved. The color filter assembly driving mechanism of a scanner according to the prior art is generally comprised of a transmission gear set coupled to the color filter assembly and driven by a DC motor. In order to achieve accurate positioning, the precision of the transmission gear set is critical, and therefore the cost of the driving mechanism becomes high. Because the color filter assembly is driven by the DC motor through the transmission gear set, the revolving speed of the DC motor is greatly reduced, and therefore a graphic matter generally has to be scanned twice. If a DC motor is used to rotate the color filter assembly of a scanner directly, synchro and in phase controls are difficult to achieve. When high speed and low speed operating modes are simultaneously provided, an expensive brake and control system shall be required. Therefore, the prior art scanners which use a DC motor and a transmission gear set to drive a color filter assembly, are generally expensive to manafacture and not satisfactory in function.